1. Field of the Invention
The invention relates to a protective device for elongated objects, and in particular to a protective device for electrical wiring, fluid lines and the like in motor vehicles.
2. Description of Related Art
A heat-protection device for elongated bodies which are exposed to heat in zones, for example for wiring in a motor vehicle, is known from WO 01/84685, which has at least a first interior heat-resistant protective layer facing the body, as well as means which carry off the heat created in the zones and distribute it over large areas.
A heat-protection element for the protection of elongated objects is disclosed in WO 99/04194, wherein the element has a first layer of an insulating material with an outer reflecting layer. Facing edges of the first layer have elements for connecting them overlappingly for forming a tube-like element. A second insulating web is arranged at the outer surface inside the edges. The second web also has a reflecting layer on its outer surface and is fastened to the first web or layer along the edges, so that air pockets are formed between the webs. A rigid monofilament wire provided in spirals is arranged inside this air pocket for further assuring the pocket-like construction. This known device is disadvantageous because it is very complicated to produce and easily loses its shape under mechanical stress.
An insulating arrangement for the insulation of heat-generating components, such as exhaust gas return lines, is known from WO 98/30830, which includes an outer layer of knit glass filament yarn. A metal wire skeleton is provided for giving the layer a tube-like shape, wherein a further layer made of a heat-insulating mineral paper is provided, which is separated from the cover layer by the metal wires. This arrangement is also disadvantageous because it is very complicated to produce.
An insulating layer for the thermal insulation of tube-like heat sources is known from WO 97/29316, wherein knit separating layers are provided, between which a metallic foil is arranged and is separated from a heat source by a knit layer. The structure of this layer includes a foil resting against the heat source, on top of it an inner knit stainless steel fiber layer, on top of that a fire-resistant paper, a second knit layer of a stainless steel fiber, and a cover layer on top of it. The complicated production of this embodiment is also disadvantageous.
It is known to enclose long or elongated bodies, for example electrical wiring or fluid lines, such as hydraulic or pneumatic lines, or pneumatic hoses, in plastic corrugated tubes as a protection against mechanical and/or thermal effects, in particular as a protection against heat and wear by abrasion. It is furthermore known to appropriately protect such elongated bodies against damage in case of an accident of the vehicle, in particular damage by squeezing or shearing.
Customary corrugated tubes are made of polypropylene or polyamide and can withstand thermal stress only to a limited degree. Consequently, such corrugated tubes do not sufficiently protect electrical wiring, hoses, or the like, which are located in vehicles near heat sources, for example near the engine, a turbo-charger, an exhaust system, exhaust gas return lines or the like, against damaging heat.
To solve this problem it is known to use highly temperature-resistant corrugated tubes made, for example, of Teflon™, or to make the insulation of the conducting wires from a highly temperature-resistant material, for example a silicon or Teflon™ material. However, such highly temperature-resistant cable insulations are very expensive. It is also known to provide glass filament hoses with a silicon sheathing.
It is furthermore known to arrange corrugated tubes of poly(tetrafluoroethylene) around cable harnesses in areas subjected to heat. However, this arrangement is disadvantageous in that a permanent heat resistance of these poly(tetrafluoroethylene) corrugated tubes is only assured up to approximately 260° C., wherein the melting point lies at 310° C., so that dammed-up heat, which often lies above 300° C., cannot be managed.
It is moreover known to laminate glass filament hoses with an aluminum foil for increasing the thermal resistance of the fiberglass hoses. However, it was noted that with the soiling of the aluminum foil resting on the glass filament hoses, which is customary in engine compartments, thermal insulation no longer exists and heat is introduced in spots into the glass filament hoses, which in these areas leads to an undesired heat transfer to the object to be protected. Furthermore, glass filament hoses coated in this way, or the coatings themselves, are very much prone to damage caused by abrasive stresses.